Re: XPath and XPattern (was Re: More on tamingSAX)
Kevin Jones wrote: >On Thursday 23 December 2004 20:26, Oleg Tkachenko wrote: > > >>It would be really nice to have such streamable XPath >>subset strictly defined (and probably with different >>name). >> >> > >My understanding is that full XPath is streamable in the >context of whole document scans, i.e. there is strictly >speaking no need to subset. The problem case is for partial >scans, i.e. XPath execution from a context node. This makes >the solution less appealing as it has less practical use, >say in XSLT. Of course subsetting XPath to make it easier >to implement in a streaming model may be a good goal >itself. > > Of course XPath is always streamable, if you have no practical limitations (e.g. you're willing to store all node data and implement unbounded look-ahead). When people speak of a "streamable subset", they mean a subset that works practically with most streaming host languages, meaning that these host languages should not have to compromise too much memory or state complexity in order to satisfy the scope of node requests from the XPath subset. In other words, everyone understands well the distinctions you're trying to point out, but we're more interested in a descriptive name than in quiddities. BTW, I don't know what you mean by "XPath execution from a context node". XPath *always* has a context node. Someone told me once that some working group was trying to define a host language for XPath that did not define a context node. I told them this is a case of people *thinking* they're using XPath, but rather using some creature of their own invention. -- Uche Ogbuji Fourthought, Inc. http://uche.ogbuji.net http://4Suite.org http://fourthought.com Use CSS to display XML - http://www.ibm.com/developerworks/edu/x-dw-x-xmlcss-i.html Full XML Indexes with Gnosis - http://www.xml.com/pub/a/2004/12/08/py-xml.html Be humble, not imperial (in design) - http://www.adtmag.com/article.asp?id=10286 UBL 1.0 - http://www-106.ibm.com/developerworks/xml/library/x-think28.html Use Universal Feed Parser to tame RSS - http://www.ibm.com/developerworks/xml/library/x-tipufp.html Default and error handling in XSLT lookup tables - http://www.ibm.com/developerworks/xml/library/x-tiplook.html A survey of XML standards - http://www-106.ibm.com/developerworks/xml/library/x-stand4/ The State of Python-XML in 2004 - http://www.xml.com/pub/a/2004/10/13/py-xml.html
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